Conventionally, linear motion guide units have been composed of an elongated guide rail or guide shaft, and a slider that fits over or conforms to the guide rail to move relatively to the guide rail in a sliding manner through more than one rolling element of ball or roller, which is allowed to recirculate through a looped circuit that is composed of a load-carrying race defined between the guide rail and the slider, turnaround passages and a return passage cut inside the slider. With the linear motion guide units constructed as stated earlier, continuous application of lubricant on or between the load-carrying race and the rolling element is indispensable to continue maintaining an adequate lubricant film around the rolling elements to keep them against metal-to-metal contact that might otherwise occur, thereby making certain of the rated lifetime of the linear motion guide unit. Most prior linear motion guide units have been ordinarily fed with lubricant every a preselected interval through any oiling port to ensure the lubricant film between the load-carrying race and the rolling element. Recently advanced machines and instruments, nevertheless, are increasingly needed to make them virtually maintenance-free from an aspect of keeping maintenance cost for lubrication reasonably less than ever. Correspondingly, the linear motion guide units incorporated in the advanced machinery are also challenged to realize the virtual maintenance-free for lubrication over a long-lasting service interval.
In Japanese Laid-Open Patent Application No. 2007-100 951 which is a commonly-assigned senior application, there is disclosed an example of the linear motion guide unit envisaged relieving the maintenance-free problem for lubrication. With the linear motion guide unit described in the commonly-assigned senior application, the application of lubricant around the rolling elements was done at the turnaround passage to make the lubrication system simpler than ever in construction, along with maintenance-free for steady and positive oil lubrication. With the prior linear motion guide unit constructed as stated earlier, a lubricant reservoir plate of a porous compact impregnated with lubricant fits into a concavity sunk below an outward end surface of the end cap. The concavity is deep pitted to open into the turnaround passage in the end cap. The porous compact impregnated with lubricant is placed in the concavity in the end cap to expose in part itself to the turnaround passage through the deep pit. Thus, the porous compact makes contact with the rolling elements running through the turnaround passage to come to supply with the lubricant around the rolling elements.
In Japanese Laid-Open Patent Application No. H10-205 534 which is also a commonly-assigned senior application, moreover, there is disclosed a linear motion guide unit having a lubricating plate which can be mounted and/or demounted out of the linear motion guide unit without any reconfiguration in the basic design specifications. With the linear motion guide unit, the lubricating plate is secured to a carriage, with lying between an end seal and a spacer member which are placed on an outward end of an end cap. The lubricating plate makes sliding engagement with at least a raceway groove on the guide rail while moving relatively to the guide rail. The lubricating plate is constituted with a sintered resinous compact of porous texture impregnated with lubricant. The sintered resinous compact is made of a sintered resinous member of finely powdery synthetic resin, which is packed in a mold and compacted under pressure together with the application of heat. The lubricating plate has dense parts and coarse parts which are placed on the lengthwise sides of the guide rail in opposition to each other and embraced together within a covering member.
With the linear motion guide unit recited in the former patent document, application or resupply of the lubricant around the rolling elements is done inside the turnaround passage in the end cap. More especially, the lubricant reservoir plate impregnated with lubricant and installed in the end cap has an applicator nose extending to be exposed in the turnaround passage through the opening pitted in the end cap. The rolling elements, while running through the turnaround passage in the end cap, come into touch with the applicator nose of the lubricant reservoir plate, thereby being lubricated with oily lubricant through the applicator nose of the lubricant reservoir plate. In the linear motion guide unit constructed as stated just earlier, however, as more lubricant than a prerequisite amount of lubricant for rolling contact between the rolling elements and the load-carrying race continues fed around the rolling elements at the early stage of the traveling operation, the lubricant preserved in the lubricant reservoir plate continues decreasing rapidly in amount down to a certain amount, and since then diminishing at roughly regular rate per unit interval. As a result, the lubricant preserved in the lubricant reservoir plate, because being consumed quickly at the early phase of the traveling operation, would reduce more rapidly, compared with an ideal state where the lubricant constantly decreases at a regular rate per unit interval ever after the early time of the traveling operation. That would raise a problem in which maintenance-free intervals become less.
Meanwhile, the advanced linear motion guide units are needed conforming to the prolonged operation with reduced maintenance schedules for lubrication in aspects of a reduction in maintenance steps on lubricant application in machines and facilities with built-in linear motion guide units, and cutting the amount of lubricant for the purpose of conserving resources and reducing environmental impact. With the linear motion guide unit that the lubricant is applied directly around the rolling elements inside the turnaround passage, it has been desired to develop the lubricant applicator capable of accumulating therein ample amount of lubricant and staving off the excessive amount of applied lubricant tending to increase at the early stage of the traveling operation suited for virtually maintenance-free operation, thereby making sure of smooth application of an adequate amount of lubricant with accompanying maintenance-free condition for lubrication.